â€œI saw them (dough bowls and grinding stones) in New Mexicoâ€ she says. â€œI was drawn to the massiveness of the forms. The dough bowls were very roughly hacked out of a solid piece of wood. The grinding stones felt as though they had just evolved into their forms through necessity. They were flat stones that became bowls over years and years of grinding grain on them. It gave the forms a gracefulness as well as a history. They seem to possess a slow movement with great power, like water moving down a river.
Double the Walls, Double the Drying
I begin with an open bowl. As I build the walls up, I begin a second wall from the floor inside of the bowl. Once these are to the height that I want, it is time to bring them together to trap air in between. The closing connection is the most crucial. Once the walls are closed, I can no longer access that inner space to reinforce joints. It must occur without having a hand inside to compress against. This can be done by having the last connection be at a place where the wall changes direction. This allows me to effectively push one surface against the other with both hands on the outside.
Once the piece is completed, trimmed, and ready to be dried, I poke a hole in the wall to allow moisture to evaporate from the inside of the piece while drying. This also relieves pressure created by the trapped air as the piece shrinks, and it serves as a release for the steam in the beginning part of the firing. I use a sewing pin so that the hole is so small that the glaze seals it up. I only need the hole during the drying and bisque; the hole is not essential during the glaze firing.
The piece is dried for the first two to three days under a layer of fabric and plastic. For the next three to six days, the piece dries under a layer of fabric only. It is best to wait at least six days before firing, so I make the double-walled pieces at the beginning of my work cycle.
If cracks form, they will be where the wall transitions from the outside to the inside. This is the case during the firing as well. For this reason, I make sure that all drying occurs slowly enough that the inside form and the outside form shrink at the same time. I fire in an electric kiln with a computer so that I can control the rate of rise in temperature.
Firing Schedule for Double-Walled Bowls
1. 80°F/hr to 205°F hold for 5-6 hours (or until there is no moisture coming off of the piece
2. 80°F/hr to 300°F hold for 10 min. (to make sure even the inside of thickest wall has reached 212°)
3. 250°350°F/hr to 1000°F (This depends on how large the piece is, the larger the piece the slower the speed.)
4. 80°F/hr to 1250°F (Slow down for quartz inversion.)
5.250°350°F/hr to 1910°F
6. 80°F/hr to 1940°F (Slow down for glazes to heal over)
Follow steps 15 for the bisque firing and use steps 26 for the glaze firing.
For further information on Jerilyn Virden, and to see more images of her work, visit www.jvirdenceramics.com.